Taco 571-2 Zone Valve

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Old 11-20-11, 08:40 PM
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Taco 571-2 Zone Valve

Hi,

I have a 4 zone FHW system run with one circulator for the heating zones and one for the HW (Superstor). One of my zones isn't circulating when calling for heat from the stat and I'm not sure if its the head or the valve itself. (The other zones are fine)

The manual lever does not work when I try that and i checked and am getting voltage across 1&2 when the stat is calling for heat and nothing when it is not.

I took the head off and pushed the plunger down with my channel locks and it moved down and up with spring tension. Does this sound like i need a new zone head to you?

Thanks!
 
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Old 11-21-11, 04:10 PM
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One thing you can do as a test is to swap one of the other heads onto the suspect body and see if you get flow...

Chances are pretty good I would say that it's the head and not the valve.

It sounds like the thermostat circuit is working (voltage readings at 1 & 2)... you might try similar readings at 2 & 3 ... with all thermostats turned down, you should have appx 24 VAC on 2 & 3, and when you turn up the suspect zone you should see that voltage go to zero. This would indicate that the valve has opened and activated the 'endswitch' in the valve.

If you get the 24VAC from the t'stat on 1 & 2 and nothing happens on 2 & 3, then the head is shot... note that it can take a few minutes for those valves to open!

Also, I think you would be able to notice that the valve head on the functioning valves is noticeably warmer than the bad one if the problem is that the heat motor has crapped out.
 
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Old 11-21-11, 05:34 PM
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If the valve handle goes down the valve is open.
 
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Old 11-22-11, 12:51 PM
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I agree with rbeck & Trooper; when the Taco 571s crap out the burned out electronics in the head usually leave a lingering stench you can detect if you get your nose close enough to the unit.
 
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Old 11-22-11, 05:01 PM
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A few ways I can think of that these valves can fail...

The heating coil can burn out, yes, it could be stinky. The valve will not open. This can happen all by itself, or it could happen because:

The 'wax filled bellows' can spring a small leak. When this happens, the valve will not open, and current will go through the heating coil continuously, eventually burning it out.

The 'endswitch' can fail. In this case, the valve will open, but the burner still will not fire up, and the circ pump will not run.

I believe that when you push down the manual lever on a Taco valve, if the endswitch is functioning, it WILL fire the burner... but I am not 100% certain of that... memory fails me often...

If pushing the manual lever down on one of the functioning zones DOES fire the boiler, and it does NOT fire on the suspect valve, then chances are that the endswitch is bad...

In any case, the head would need replaced.

Here's a little light reading for ya:

http://www.taco-hvac.com/uploads/Fil...ry/102-076.pdf

http://www.taco-hvac.com/uploads/FileLibrary/100-3.pdf
 
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Old 11-23-11, 07:17 AM
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Originally Posted by NJ Trooper View Post
I believe that when you push down the manual lever on a Taco valve, if the endswitch is functioning, it WILL fire the burner... but I am not 100% certain of that... memory fails me often...
Hello Mr. NJ,
This is definitely not the case with the older Green Head Taco's. I'm not sure about the Gold ones but i think they act the same.

Edit to add: At least not with ZVC50x control.

Peter
 
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Old 11-23-11, 01:23 PM
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Thanks

Hi,

i appreciate everyone's feedback. For some reason, i was banned for my username and couldn't get back onto the forum without setting up a new email address and re-registering with a new username!!

Anyway, the only other item i forgot to mention was when the heating season kicked in, I had an excessive amount of air in the system and bled it off. The pressure in the system was very low (10psi....i normally run around 23psi) and i added water manually with the make up valve, which must have been sticking. Anyway, it was about then that i noticed that this zone wasn't working and i wonder if the amount of air in the system could have caused the valve to fail?

I did notice that the motor head was warm when i was looking at it the other night. Warm as if it was getting current like NJ Trooper was referring to, and not because it was heated by circulated water. None of the zones were calling for heat (except that one)and all pipes were stone cold.

I'll switch out the bad one with a good one and see if that helps.

Thanks again everyone, i'll post again tonight.
 
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Old 11-23-11, 02:55 PM
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i wonder if the amount of air in the system could have caused the valve to fail?
Most likely not... but what you have just said does make me wonder about something...

You say that one zone is not circulating...

But this could also be a symptom of air blocking that loop.

So, let me ask this:

When the thermostat for that zone calls for heat, does the circulator pump run? Does the boiler fire? I don't think we've gotten a clear picture of the exact symptom yet.
 
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Old 11-23-11, 03:01 PM
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Just to clarify a little more:

If the boiler fires and the circ pump runs when that zone calls for heat, the valve and head are probably both fine, and the problem is likely an air block in that loop.

If nothing happens when there's a heat call, then of course, the valve head is probably bad.
 
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Old 01-08-12, 08:54 PM
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Sorry that my post is so delayed. Trooper, you were right. it was air in that loop and after i swapped out a good head with the non-functioning zone head and no change, I isolated that zone as best as i could and purged the zone. Lots of air and hot water right behind it......happy ending.

I guess you should always start with the simple stuff first!

Thanks for all your help, I really appreciate it!
 
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